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| United States Patent |
5,170,302
|
|
Matsumoto
|
December 8, 1992
|
Thin-film magnetic head with multiple interconnected coil layers
Abstract
A thin-film magnetic head comprising four or more conductive coil layers
each wound spirally and alternately piled up so as to form a lamination
structure. The conductive coil layers are divided into first and second
groups so that the total number of turns of the conductive coil layers in
the first group becomes equal to the total number of turns of the
conductive layers in the second group. The conductive coil layers in the
first group are coupled in series to each other and the conductive coil
layers in the second group are also coupled in series to each other, the
first and second groups being coupled in series to each other and a center
tap being provided between the first and second groups.
| Inventors:
|
Matsumoto; Toshio (Kanagawa, JP)
|
| Assignee:
|
Mitsubishi Denki Kabushiki Kaisha (JP)
|
| Appl. No.:
|
693794 |
| Filed:
|
April 30, 1991 |
Foreign Application Priority Data
| Current U.S. Class: |
360/123; 360/126 |
| Intern'l Class: |
G11B 005/17 |
| Field of Search: |
360/123,126
|
References Cited
U.S. Patent Documents
| 4639811 | Jan., 1987 | Diepes et al. | 360/123.
|
| 4694368 | Sep., 1987 | Bischoff et al. | 360/123.
|
| 4713711 | Dec., 1987 | Jones, Jr. et al. | 360/123.
|
| 5047886 | Sep., 1991 | Toyoda et al. | 360/126.
|
| Foreign Patent Documents |
| 0213687 | Mar., 1987 | EP.
| |
| 0255523 | Nov., 1986 | JP.
| |
| 0063114 | Mar., 1988 | JP.
| |
Primary Examiner: Severin; David J.
Attorney, Agent or Firm: Wolf, Greenfield & Sacks
Claims
What is claimed is:
1. A thin-film magnetic head comprising five or more insulating layers and
four or more conductive coil layers placed between a lower magnetic pole
and an upper magnetic pole and alternately piled up so as to form a
lamination structure, said conductive coil layers being respectively would
spirally and placed on surfaces of said insulating layers, characterized
in that the number of turns of said conductive coil layers is reduced
toward the upper layer, said conductive coil layers are divided into first
and second groups so that the total number of turns of the conductive coil
layers in said first group becomes equal to the total number of turns of
the conductive layers in said second group, the conductive coil layers in
said first group are coupled in series to each other and the conductive
coil layers in said second group are coupled in series to each other, said
first and second groups being coupled in series to each other and a center
tap being provided between said first and second groups.
2. A thin-film magnetic head as claimed in claim 1, characterized in that
the conductive coil layers in said first or second group are arranged such
that one i in series coupled to the other with the conductive coil layer
adjacent thereto being jumped over.
3. A thin-film magnetic head as claimed in claim 1, characterized in that
the number of turns of coils in said conductive coil layers i successively
decreased by one or a predetermined number toward the upper layer.
4. A thin-film magnetic head as claimed in claim 1, characterized in that
the number of turns in coils of said conductive coil layers is irregularly
decreased toward the upper layer.
5. A thin-film magnetic head as claimed in claim 1, characterized in that
the coil pitches in the conductive coil layers are substantially equal to
each other or changed to be greater toward the upper layer.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to thin-film magnetic heads for use
in magnetic disk apparatus, and more particularly to such a thin-film
magnetic head having four or more conductive coil layers.
2. Description of the Prior Art
In order to meet the requirement of high-density recording of information,
the track width of a magnetic head is being narrowed increasingly. On the
other hand, in response to the track width being narrowed to decrease the
output, the thin-film magnetic head is arranged so as to be equipped with
a plurality of conductive coil layers to increase the number of turns in
the winding to enlarge its output and to be provided with a center tap for
the winding to counter increase in the inductance accompanying the
increase in the number of turns. For instance, as illustrated in FIG. 9,
such a thin-film magnetic head is arranged such that insulating layers 3
made of an organic insulating material and conductive coil layers 4 are
provided between a lower magnetic pole 1 and an upper magnetic pole 2 to
be alternately piled up so as to form a laminated body which is placed on
a base 6 with a gap member 5 being interposed therebetween.
A further description will be made hereinbelow in terms of the insulating
layers 3 and the conductive coil layers 4. On the upper surface of the gap
member 5 there is placed the first insulating layer 3a, and on the upper
surface of the first insulating layer 3a there is disposed the first
conductive coil layer 4a. Further, successively piled up are the second
insulating layer 3b, second conductive coil layer 4b, third insulating
layer 3c, third conductive coil layer 4c, fourth insulating layer 3d,
fourth conductive coil layer 4d and fifth insulating layer 3e. The lower
magnetic pole 1, conductive coil layers 4a to 4d and upper magnetic pole 2
are respectively insulated by means of the first to fifth insulating
layers 3a to 3e. In addition, although not illustrated, the first
conductive coil layer 4a and second conductive coil layer 4b, the second
conductive coil layer 4b and third conductive coil layer 4c, and the third
conductive coil layer 4 c and fourth conductive coil layer 4d are at their
end portions coupled to each other, respectively. Moreover, a center tap
is drawn from the connection point between the second and third conductive
coil layers 4b and 4c, and lead lines are respectively provided at the
other end portions of the first and fourth conductive coil layers 4a and
4d.
Here, for the thin-film magnetic head having the center tap, since two coil
portions divided by the center tap are required to be coincident in
resistance and inductance with each other (see the Japanese Patent
Laid-Open Publication Nos. 61-255523 and 63-63114), the conductive coil
section comprising the first and second conductive coil layers 4a, 4b and
the conductive coil section comprising the third and fourth conductive
coil layers 4c, 4d are generally arranged so as to be equal in the number
of turns in the coil and the width of the coil to each other. In addition,
when piling up the respective conductive coil layers, a height difference
appears with respect to the circumference, and because limitation is
imposed upon the mask engraving on manufacturing, the respective
peripheral ends of the conductive coil layers 4a to 4d and the insulating
layers 3a to 3e are required to be successively reduced from the lower
layer to the upper layer so as to incline the circumferential surface as a
whole, thus more decreasing the coil pitch of the conductive coil layer as
the position becomes higher.
There is a problem which arises such a conventional thin-film magnetic
head, however, in that, as the number of the coil layers increases, the
height difference increasingly enlarges with respect to the peripheral
portions so as to make severer the engraving condition. Moreover, the coil
pitch become smaller as the position becomes higher to reduce the space
between the coils. This also make more difficult the engraving.
Although the Japanese Patent Laid-Open Publication No. 63-63114 discloses a
multilayer balance-winding thin-film magnetic head where the respective
coil layers are formed by a bifilar and a midpoint terminal is provided so
that two coil sections are coincident in the number of turns and the width
of the coil with each other and steps disappears at the circumferential
end portions of the coil layer and the insulating layer, since in this
magnetic head two conductive coils are simultaneously provided in parallel
to each other by the bifilar, the outside length becomes greater than the
inside length and hence the resistance of the outside conductive coil
section becomes higher, whereby the electromagnetic characteristics of the
two conductive coil sections divided by the midpoint terminal becomes
unbalanced.
SUMMARY OF THE INVENTION
The present invention is for eliminating the above-described problems and
contemplates to provide a thin-film magnetic head which is capable of not
only enlarging the coil pitch irrespective of an upper layer portion to
make easy the engraving but also equalizing the resistance and inductance
of two coil sections divided by a center tap.
According to the present invention, all of the conductive coil layers are
divided or classified into first and second groups so that the sum of the
numbers of turns of the conductive coil layers in the first group becomes
equal to the sum of the numbers of turns of the conductive coil layer in
the second group, and the conductive coil layers in the first group are
coupled in series to each other and the conductive coil layers in the
second group are also coupled in series to each other, and the first and
second groups are coupled in series to each other, and further a center
tap is provided between the first and second groups.
The above and other objects, features, and advantages of the invention will
become more apparent from the following description when taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view showing a principal portion of an
embodiment of a thin-film magnetic head according to the present
invention, FIGS. 2 and 3 are illustrations of conductive film patterns of
the respective conductive coil layers of the thin-film magnetic head shown
in FIG. 1, FIGS. 4 to 8 are illustrations of another embodiment of a
thin-film magnetic head according to this invention, and FIG. 9 shows a
conventional thin-film magnetic head.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention will first be described with reference to an
embodiment illustrated in FIGS. 1 to 3 where parts corresponding to those
in FIG. 9 showing the conventional thin-film magnetic head are indicated
by the same marks. The description thereof will be made principally in
terms of its feature. FIG. 1 is a cross-sectional view showing a principal
portion of the embodiment of a thin-film magnetic head according to this
invention, and FIG. 2 illustrates conductive film patterns of the
respective conductive coil layers constituting the FIG. 1 thin-film
magnetic head where dotted lines and arrows represent the connection
state. FIG. 3 is an illustration useful for a better understanding of the
connection state.
As illustrated in FIGS. 1 to 3, the thin-film magnetic head of this
embodiment is arranged such that between a lower magnetic pole and an
upper magnetic pole are provided insulating layers 3 made of an organic
insulating material and conductive coil layers 4 which are alternately
laminated. These lower magnetic pole 1, insulating layers 3 conductive
coil layers 4 and upper magnetic pole 2 are placed on a base 6 with a gap
member 5 being interposed therebetween. For formation, each of the first
to fourth conductive coil layers 4a to 4d is wound spirally and placed on
a flat portion of the upper surface of each of the insulating layers 3a to
3d. In this case, the numbers of turns of the respective coils are
arranged to be different from each other, that is, the numbers of turns
thereof are 9, 8, 7 and 6 in order from the lower layers. Further, the
lower magnetic pole 1, conductive coil layers 4a to 4d and upper magnetic
pole 2 are insulated by means of the respective insulating layers 3a to
3e, respectively.
Although not illustrated, the respective conductive coils between the first
and fourth conductive coil layers 4a and 4d, the fourth and second
conductive coil layers 4d and 4b and the second and third conductive coil
layers 4b and 4c are at their end portions coupled to each other, and a
center tap is led from the connection portion between the second and
fourth conductive coil layers 4b and 4d and a lead wire is led from the
non-connected end portion between the first to third conductive coil
layers 4a and 4c.
A further description will be made hereinbelow in terms of the
above-mentioned conductive coil layers 4a to 4d with reference to FIGS. 2
and 3. The respective conductive coil layers 4a to 4d are formed with
conductive films having patterns as illustrated in FIG. 2. That is, in the
first conductive coil layer 4a, a lead wire 41 is formed at an outer end
portion of the coil and a connection portion 42a to the fourth conductive
coil layer 4d is formed at an inner end portion of the coil. In the second
conductive coil layer 4b, a lead wire 43a which is a connection portion to
the fourth conductive coil layer 4d and further to the center tap is
formed at an outer end portion of the coil and a connection portion 44a to
the third conductive coil layer 4c is formed at an inner end portion of
the coil. Further, in the third conductive coil layer 4c, a lead wire 45
is disposed at an outer end portion of the coil and a connection portion
44b to the second conductive coil layer 4b is disposed at an inner end
portion of the coil. Still further, in the fourth conductive coil layer
4d, a lead wire 43b which is a connection portion to the second conductive
coil layer 4b and further to the center tap is provided at an outer end
portion of the coil and a connection portion 42d to the first conductive
coil layer 4a is provided at an inner end portion of the coil. In
addition, near the connection portions 44a and 44b of the respective inner
end portions of the second and third conductive coil layers 4b and 4c,
there are formed connection portions 42b and 42c for coupling the
connection portion 42a of the inner end portion in the first conductive
coil layer 4a to the connection portion 42d of the inner end portion in
the fourth conductive coil layer 4d. That is, the first and fourth
conductive coil layers 4a and 4d not adjacent to each other but opposed to
each other with the conductive coil layers 4b and 4c being interposed
therebetween are in series coupled to each other so as to form the first
group, and remaining second and third conductive coil layers 4b and 4c are
in series coupled to each other so as to form the second group. The first
and second groups are in series coupled to each other through the lead
wires 43a and 43b. In this case, the total number of turns of the coils of
the conductive coil layers 4a and 4d in the first group is 15 and the
total number of turns of the coils of the conductive coil layers 4b and 4c
is 15. They are equal to each other.
In the thin-film magnetic head thus arranged, the total number of turns is
30, while the center tap causes division into first and second group coil
sections, the first group coil section comprising the first and fourth
conductive coil layers 4a and 4d and the second group coil section
comprising the second and third conductive coil layers 4b and 4c. In the
former the number of turns is 15 and in the latter the number of turns is
15, the former being equal in the number of turns to the latter. That is,
with the center tap being provided between the first and second groups,
they become coincident in resistance and inductance with each other.
Accordingly, according to this embodiment, the numbers of turns of the
first to fourth conductive coil layers 4a to 4d can be successively
reduced so as to be 9, 8, 7 and 6 in order from the lower layer toward the
upper layer. As a result, even in the case of the upper layer, the number
of turns thereof is relatively large so that the coil pitch is not
required to be narrowed, thereby allowing easy mask engraving.
Here, if in the first to fourth conductive coil layers 4a to 4d the numbers
of turns are successively reduced by one toward the upper layer as
illustrated in FIG. 4, the same effect can be achieved. Further, even if
successively reduced by two or more toward the upper layer as illustrated
in FIG. 5, the same advantage can be obtained. Still further, even if the
number of the conductive coil layers is 8 as shown in FIG. 6, the same
effect can be obtained with the similar connection. In addition, even if
the number of turns irregularly varies toward the upper layer as shown in
FIGS. 7 and 8, the same advantage can be achieved with the similar
connection technique. In FIGS. 7 and 8, the numbers of conductive coil
layers are 5 and 6 and the connection systems are arranged to be different
from those in FIGS. 3 to 6.
For all of the conductive coil layers, the coil pitches and spaces between
the coils are not always required to be equal to each other. By taking
into account the ease of the coil engraving, it is possible to determine
the coil pitchs to be more enlarged toward the upper layer. Further, it is
possible to suitably determine the form and position of the center tap,
lead wires and connection portions.
According to this invention, since the upper conductive coil layer can be
arranged to have a coil pitch substantially equal to that of the lower
conductive coil layer or the coil pitch can be gradually increased toward
the upper layer, it is possible to provide a thin-film magnetic head which
is easy in engraving concurrently with equalizing the resistances and
inductances of the coil sections to be divided by the center tap. PG,13
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